Remove unnecessary nunique function in Series.

[martinfalisse]

Removes unnecessary nunique function in Series, as indicated by @vyasr here #10077 (comment).

Seem to have made a mistake when correcting the style of my last commit and not have kept the original changes of that commit.

[GPUtester]

Can one of the admins verify this patch?

[quasiben]

ok to test

[vyasr]

Ack @martinfalisse and this is why we don't force push :) Thank you for the quick fix!

[codecov]

Codecov Report

Merging #10205 (a02915f) into branch-22.04 (a7d88cd) will increase coverage by 0.05%.
The diff coverage is 0.00%.

❗ Current head a02915f differs from pull request most recent head 3c9d7e7. Consider uploading reports for the commit 3c9d7e7 to get more accurate results

@@               Coverage Diff                @@
##           branch-22.04   #10205      +/-   ##
================================================
+ Coverage         10.42%   10.47%   +0.05%     
================================================
  Files               119      122       +3     
  Lines             20603    20501     -102     
================================================
  Hits               2148     2148              
+ Misses            18455    18353     -102     

Impacted Files	Coverage Δ
python/cudf/cudf/core/_base_index.py	0.00% <ø> (ø)
python/cudf/cudf/core/column/categorical.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/column/column.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/column/datetime.py	0.00% <ø> (ø)
python/cudf/cudf/core/column/numerical.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/column/string.py	0.00% <ø> (ø)
python/cudf/cudf/core/column/timedelta.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/column_accessor.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/dataframe.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/frame.py	0.00% <0.00%> (ø)
... and 17 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a25a2ec...3c9d7e7. Read the comment docs.

[vyasr]

@gpucibot merge